background for a page

Im trying to work on a page background with your theme, to explain my intentions I’ll pins some drawnings

Grey is the background I want all under the black toolbar/menu, and after that those pink “containers” have to stay white, so
https://prnt.sc/slvsej

make the background and containers look similar to that
https://prnt.sc/slvsuh

I don’t even know if that is possible with your theme to make it just on 1 page, was following the manual

as in this picture there is a background image, grey internal background and I pointed a white container, different from the others.
https://prnt.sc/slvvyh

so I thought some ways it’s possible. Tried to be as clean as possible to explain my intention, thenks in advance

The page I need help with: [log in to see the link]